Developments in the industry of electronics place continued pressure on those of skill in the art to develop new technologies. One specific ongoing demand, which is related to miniaturization, is the need for solid electrolytic capacitors with ever increasing lower resistance and lower inductance.
Inductance in a solid electrolytic capacitor is mainly the result of excessive current loop area, or loop size, between the anode terminal and cathode terminals. This loop is represented by the electrical path required to complete a circuit through the capacitor.
Many methods have been employed in the industry to lower resistance and inductance such as those methods taught in U.S. Pat. No. 8,344,735 and U.S. Pat. No. 8,254,087 each of which is incorporated herein by reference. In these methods a substrate is manufactured with the conductive terminals in place and the capacitor element is attached to the conductive terminals of the substrate. This process increases the manufacturing cost and results in lower physical reliability. Producing the substrate structure is typically more expensive than the traditional lead frames used in the manufacture of solid electrolytic capacitors. Furthermore, the interface between the substrate and encapsulating resin can result in significantly reduced package integrity relative to encapsulated lead frame devices.
Other methods involve a leadframe material exposed from the bottom of the encapsulating resin as taught in commonly assigned U.S. Pat. No. 6,262,878 which is incorporated herein by reference. This method provides lower inductance but at the expense of production cost and the terminations are not in compliance with industries standards. The high cost and non-standard terminations are both undesirable. Having a leadframe structure exposed below the encapsulating resin requires a change in equipment and additional processes which is highly undesirable. Furthermore, the package integrity is compromised. Since the leadframe is only secured into the encapsulating resin by the edges of the leadframe the leadframe is more susceptible to sheer stresses.
In spite of the ongoing effort those of skill in the art still seek improvements in capacitors, and particularly, improvements in the inductance, ESR and resistance characteristics of capacitors.